Questions tagged [centroids]

In geometry, the centroid, geometric center, or barycenter of a plane figure or two-dimensional shape X is the intersection of all straight lines that divide X into two parts of equal moment about the line. Informally, it is the "average" (arithmetic mean) of all points of X. The definition extends to any object X in n-dimensional space: its centroid is the intersection of all hyperplanes that divide X into two parts of equal moment.

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1answer
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Polygon Centroid Options and Appropriateness (FeatureToPoint, Labels, etc)?

I've found a couple of other Stack Exchange questions related to this, but they were not satisfying. For example: How does ArcGIS Desktop calculate INSIDE point for Feature to Point? does not tell ...
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How to find multiple centers of gravity?

Say I have a number of customers in a geographical area, marked "c": Each customer has a Lat/Long. I would like to find x number of points, in the same space, that best serve the customers, ie. they ...
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Calculate The Minimum Distance from Polygon Centroid to Edge

I am looking to calculate the minimum distance from the Center of a polygon (A crescent shaped polygon would have a center inside the polygon) to its edge. I have parcel data and I am trying to ...
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Obtaining Centroid from Polygon in SQL Server 2008 R2

I have several spatial layers created in QGIS that are held as spatial data in SQL Server 2008 R2. What I want to do is to find the centroid (OS Easting and Northing) of the polygon from the geometry. ...
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How to select centroid of multiple nearby points with same attribute

This question is very similar to #131823, that is not solved yet. I want to merge several points like bus stops into one single point in the centroid of all selected points. The bus stops have a ...
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How exactly is the centroid of polygons calculated?

I would like to know how exactly QGIS Geometry tools -> polygon centroid is calculating the point coordinates. For example does it divide the boarder of the polygon into small points, take two pairs ...
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How to add Lat/long columns to a point layer which is not in WGS84? [duplicate]

I need to extract the Lat/long coordinates of the centroids of districts. My QGIS project SCR and the different layers have all been set on "WGS 84 / UTM zone 18N". I've created the centroids using ...
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Identify polygons greater than n-th percentile and perform further analyses using arcpy

My goal is to identify tracts that are above the 99 percentile of a variable (xvar), to dissolve contiguous tracts by summing a variable (yvar), and to get the coordinates of the centroids (...
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Zip + 4 Centroids

I have a data set with ZIP +4 codes, and ideally, I'd like to map them (their centroids) as points. I'm not interested in their boundaries (since they're not really geographies anyway). Does anyone ...
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How does ArcGIS Desktop calculate INSIDE point for Feature to Point?

Let me back up and say that from what I understand there are two common ways to calculate the centroid of a polygon in ArcGIS Desktop: Using Calculate Geometry on fields within the attribute table of ...
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Finding centroids for icosahedral gnomonic projection?

I've been trying to create an icosahedral gnomonic projection, like this example by Jason Davies or this one (the Fisher projection). The method that I initially used was using the centroid of each ...
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Distance to nearest hub output not correct

In QGIS 2.6, I'm working with two point layers: center of the population per census tract and stores that accept food stamps. I'm using "distance to nearest hub" to calculate nearest food stamp outlet ...
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Error adding feature to centroids in QGIS [closed]

I want to map forest stands. I have the compartments as centroids and I am trying to add a feature by snapping to them and creating polygons. Each time I click, however, it displays a box titled "...
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How to move a point shapefile to the centroid of a polygon?

I have this point shapefiles on top of a bounded polygon. I would like to move each point to the centroid of each bounded polygon. Is there an automatic way in ArcGis 10.1 of solving this? Like in the ...
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Combining different geometry types into same feature class?

I've searched the question in this blog. Maybe I don't use the right words but anyway my problem is not present in any post so I'll try to explain my question by opening a new one. I have a polygon ...
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Shortest distance from polygon centroids to a line in QGIS

To get the distance of each polygon centroid from a line, I have tried the Distance to nearest hub algorithm from the Processing Toolbox. The distances I got from the algorithm did not seem correct, ...
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How can I find the center of the circle or ellipse I just created

I need to draw circles and ellipses with a certain length/width/ radius. I used the rectangles ovals digitizing plugin to create them, but only measured roughly the circles' radiuses. It would be ...
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How to compute weighted centroids in PostGIS?

I have a group of points and each point has an associated count value. How can I calculate the centroid of the group weighted by the values associated to each point?
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Looking for information on methods or algorithms used to calculate centroid from polygons across software

Looking for information on methods or algorithms used to calculate point centroids from polygons across software. ArcGIS uses a "gravity model" but can someone point me to the math or a paper on the ...
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OpenLayers: How to get *real* centroid of a Line Geometry/Feature?

I have declared a line geometry as: var lineString = new OpenLayers.Geometry.LineString([source,target]); then I am trying to get the centroid of this lineString as lineString.getCentroid(). But ...
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Calculating Centroids with Zonal Geometry in ArcGIS

I have a shapefile containing polygons. Each polygon is defined by its postal code. I want to calculate the centroid of each polygon using Zonal Geometry. Sadly, for some polygons there are no ...
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assign and move centroids to their polygons

I m using QGIS 1.8 Lisboa. After calculating the centroids from a polygon shapefile, if some of them lie outside the polygon outlines, I'd like to move them on the polygon they came from. The ...
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Qgis creating point within complex shapes (with holes) [duplicate]

I'm looking for a tool to create a point in every polygon, that will be placed in the polygon. these are complex shapes with holes. the point must not put in those holes! the "plugin RealCentroid" ...
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Find the vertices of an ROI in XROI using IDL

I need to find the vertices of an ROI shape created in IDL's XROI, so that I can redraw the ROI on multiple images. I know you can find the centroid, area and perimeter with the GEOMETRY command, but ...
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Is there a method in SQL Server (2008 or 2012) that will return the equivalent of the Esri LabelPoint for geometry?

I'm looking for a method that is equivalent to the Esri LabelPoint for SQL Server Geometry (or fairly close). Does it exist by a different name? Or is there an after-market implementation? I found ...
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1answer
646 views

How to get projected centroids in QGIS?

I am trying to get a centroid for several polygons on a global scale, in a way that it would correctly represent the common centre of all the polygons, taking Earth's curvature into account. The ...
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How to calculate centroid of a polygon defined by a list of longitude/latitude points? [duplicate]

I've imported some polygons (ways) from OpenStreetMap and now want to calculate the centroids of them. For this purpose I wrote following code: final List<Point2D.Double> points = ...
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Locating the centroid (center of mass) of spherical polygons

I'm trying to work out how best to locate the centroid of an arbitrary shape draped over a unit sphere, with the input being ordered (clockwise or anti-cw) vertices for the shape boundary. The density ...
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How do I convert longitude & latitude to a 3d (geocentric x,y,z) coordinate?

I'm interested in finding the centroid of a point cloud. I understand that to do this I need to convert latitude and longitude values to 3d coordinates, average them and then convert the resulting ...
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How to obtain Census Tract Centroids when Bureau's web site unavailable?

Does anyone have the Census Bureau file of census tract centroid, for either 2000 or 2010 tracts? With the Bureau's web site shut down, the only available file is the EPA's, and it omits about 500 ...
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How to use the field calculator's centroid() Geometry function in qgis 2.0?

There is an option in the field calculator for centroids under geometry which when you double click gives you "centroid( ". What information is required here in order to use this function?
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How to convert polygons to centriods without losing attribute names?

I have a GeoJSON file of polygons and I need to convert it to centroids. Finding the centroid is very easy in QGIS. Problem My attribute names are very long and have a colon between them, e.g. ...
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How to use centroid option in Field Calculator in QGis

I want to use Centroid option in field calculator in QGis .How to access it?
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Finding the “center of gravity” of multiple points where points have unequal weights [closed]

I'm trying to reduce a set of lat/lons (each with it's own weight) into one lat/lon that is the center of mass of all of the points. however when I map the results the average point falls no where ...
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0answers
359 views

Centroid of the equator and a point

Suppose I already have a way to compute the centroids of different geometry types: Points (arithmetic mean of Cartesian coordinates). Linestrings (polylines) (weighted mean of segment mid-points in ...
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Calculating a spherical polygon centroid

I'd like a general way to calculate centroids for polygons on a sphere. So far, the best online reference appears to be: Tools for Graphics and Shapes by Jeff Jenness. The method described there ...
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2answers
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Is it possible to extract Coordinates of Polygon Centroid in QGIS?

I have created polygon centroids using one of the "Geometry Tools" but I would like to extract the actual coordinates into Excel for further work. Is this possible?
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1answer
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table of polygon centroids

Given a polygon layer, census tracts, how can I generate a table of centroid coordinates in QGIS, or add columns with the centroid coordinates or generate a new layer of polygon centroid points?
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3answers
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Find polygon centroid with Python

I'm using ArcGIS 9.3 to find centroid of some polygon features. I'd like to do this in Python, but so far I can only find solutions with VBA. Can anyone provide some leads here?
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1answer
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How to find polygons centroids? [duplicate]

Possible Duplicate: Get list of coordinates for points in a layer? Sorry for another basic question - my map is almost done but now my boss wants me to enter new outbreaks (that we don't have ...
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Formula to get polygon centroid

I need to compute the centroid position of an irregular polygon with lat and lon coordinates in Java. Which formula should I use to correctly compute a centroid?
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How to place multiple symbols on one polygon centroid?

I am using QGIS for visualizing the health conditions of elderly living in an old age home, some of the elderly have multiple medical device with them and I want to show them on the map. Suppose I ...
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Is it possible to query a MySQL database using the results from map.getBounds() with Google Maps API v3?

I have a MySQL database that contains a large number of polygons, one for each district on a map. They are all quite complicated and it's unrealistic to simply load them all at once. I've looked into ...
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How can I calculate the center point inside a polygon in ArcGIS 9.3?

I'm using the JavaScript API 1.6 on ArcGIS 9.3. I have a polygon geometry in an ArcGIS map, and I'm trying to find a way to get the point that lies in the exact center of the geometry. What is the ...
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1answer
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How to force QGIS Centroid Fill inside the Polygon?

I would like to use a centroid fill to enable me to place a letter inside a polygon. The advantage of using a centroid fill is that it also shows up in a legend, whereas labelling the layer would mean ...
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How do I calculate a weighted centroid with respect to a raster, e.g. population weighted centroid

In ArcGIS 10.0, how do I calculate the weighted centroid of a collection of polygons, where I want the weight to be a raster layer. In particular I am using a raster of population counts and would ...

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